Thick film or cermet resistor materials are often utilized in variable resistors or potentiometers. Thick film resistors generally comprise an amorphous ceramic material containing a predetermined quantity of a conductive metal or metallic oxide with the amount of the metallic material determining the electrical resistivity of the resistor element. Examples of such resistors are described in U.S. Pat. No. 2,950,995, Place et al., Aug. 30, 1960; U.S. Pat. No. 2,950,996, Place et al., Aug. 30, 1960; U.S. Pat. No. 3,052,573, Dumesnil, Sept. 4, 1962; U.S. Pat. No. D'Andrea, Feb. 9, 1960; U.S. Pat. No. 3,304,199, Faber et al., Feb. 14, 1967; and U.S. Pat. No. 3,899,499, Pukaite Aug. 12, 1975 assigned to the assignee of the present invention.
A problem with the use of cermet resistors in potentiometers or variable resistors exists with regard to excessive contact resistance between the contact wiper and the resistor element. Variations in the contact resistance also result in electrical noise. Additionally, excessive wear of the resistor and/or wiper contact is a problem. Various attempts have been made to eliminate the aforesaid problems as evidenced by the U.S. Pat. No. 3,597,720, Burgess Aug. 3, 1971; and U.S. Pat. No. 3,717,837, MacLachlan Feb. 20, 1973. MacLachlan teaches the use of a diffused layer of gold on the contact surface of a thin film cermet resistor to reduce contact noise. Burgess teaches the use of a conductive resinous polymerizate wiper contact.